Volfson's craft is theoretically powered by a superconductor shield that changes the space-time continuum in such a way that it defies gravity. The design effectively creates a perpetual-motion machine, which physicists consider an impossible device.

Journalist Philip Ball reported on the newly patented craft in the current issue of the science journal Nature.

Robert Park, a consultant with the American Physical Society in Washington, D.C., warns that such dubious patents aren't limited to the antigravity concept.

"I might hear a complaint about a particular patent, and then I look into it," he explained. "More often than not it's a screwball patent. It's an old problem, but it has gotten worse in the last few years. The workload of the patent office has gone up enormously."

Some people might consider patents on unworkable products to be relatively harmless. Park, a physics professor at the University of Maryland at College Park, disagrees.

"The problem, of course, it that this deceives a lot of investors," he said. "You can't go out and find investors for a new invention until you can come up with a patent to show that if you put all this money into a concept, somebody else can't steal the idea, according to National Geographic.

The interesting thing about the invention is that it defies the laws of physics and is put in the same league as a perpetual motion machine.

The main problem with inventing such a machine is that it implies the availability of unlimited energy, which it is unlikely that Mr Volfson has managed to do yet.